Definetly need to run 91 or greater octane at all times or you risk tearing up the motor, especially under boost. As long as the plugs are NOT Platinum plugs then you should be fine. Stock irridium or copper only.
I'd check for vac leaks even though you say its not showing any signs of one. Often the "T" under the supercharger snout likes to crack and cause issues. I'd fire it up and hit all the vac line connections with some carb cleaner and see if the motor stumbles/changes tone. If so then there's a leak.
When you replaced the crank and main bearings, did you have the block align bored or just stick a new crank in it?
